Syrian Democratic Forces fighters north of Raqqa, Syria, as the coalition moves to recapture the city from Isis.
Photograph: Rodi Said/Reuters

Arab forces will lead the fight to recapture Raqqa from Islamic State, the US has said, as it seeks to soothe Turkish concerns that Kurdish troops could take over the predominantly Sunni Arab city in Syria.

Ankara, which wants to prioritise the removal of the US-backed Kurdish YPG forces from northern Syria, has reiterated its hostility towards the involvement of Kurds in the Syrian Democratic Forces, the coalition of Kurdish and Arab fighters that has been on the offensive in the area.

Turkey views the YPG (Kurdish People’s Defence Units) as an arm of the PKK, which has been waging a decades-long insurgency in the south-east of Turkey. It wants to ensure that the YPG cannot knit Kurdish enclaves in northern Syria into a de facto state that could strengthen the PKK.

In an effort to manage the deepening conflict between its two warring allies, and reassure the Turks, the chairman of the US Joint Chiefs of Staff, Joseph Dunford, said he did not think the YPG would be involved in the direct capture of the town, but only in its isolation, a process that he said may take months.

He also suggested Turkish views would be taken into account before any final assault, which in any case is not likely to occur for many months.

“The coalition and Turkey will work together on the long-term plan for seizing, holding and governing Raqqa,” Dunford said.

The SDF has been on the offensive in the area since late Saturday, aiming to initially isolate and encircle Raqqa, which has been under Isis control since 2014. The US-led coalition has said it will provide air support, signalling at the minimum that the US wants to put simultaneous pressure on the extremists in Raqqa and in their other urban stronghold of Mosul, in Iraq.

Joseph Dunford, chairman of the US Joint Chiefs of Staff. Photograph: Cliff Owen/AP

“The SDF is making sure the IS forces that are in Mosul cannot reinforce the IS forces in Raqqa, and that the force in Raqqa cannot conduct external operations into Turkey, into Europe and into the United States,” Dunford said.

He added: “We always knew the SDF wasn’t the solution for holding and governing Raqqa. What we are working on right now is to find the right mix of forces for the operation.”

The right mix is for local tribes and other people from the vicinity of Raqqa to spearhead the operation and remain to hold and govern the city once it is taken from Isis, Dunford said.

“[The operation needs] a predominantly Arab and Sunni Arab force,” he said. “And there are forces like that. There is the moderate Syrian opposition, the vetted Syrian forces and the Free Syrian Army forces, and there is some initial outreach to forces in Raqqa proper.”

He was speaking after meeting his opposite numbers in the Turkish military in Ankara, at which he promised to be completely transparent with the Turks about the Raqqa operation by embedding Turks in the planning operation.

Turkey’s deputy prime minister, Numan Kurtulmuş, said on Monday the Turkish priority was to limit Kurdish advances in Syria.

Using non-Arab elements to drive Isis out of Raqqa would not contribute to peace in the region, he said. He argued that Sunnis in Raqqa, regardless of their dislike of Isis, would not welcome a Kurdish liberation force.

Kurtumuluş also added that “legitimacy cannot be obtained through a terror organisation brandishing arms” and that the “United States will sooner or later see this reality”.

The Raqqa operation is in part designed to reduce Isis options as Iraqi Kurdish peshmerga forces join others in trying to storm Isis-held towns north-east of Mosul.

The Iraqi operation, involving a 100,000-strong alliance of troops, security forces, peshmerga and Shia fighters backed by US-led airstrikes, has made inroads to the south of Mosul and entered the city from the east. Progress inside the city will be dependent on the quality of intelligence the Iraqi forces gather from the local population, so the army is moving slowly.

US-led airstrikes against Islamic State in Syria and Iraq – interactive

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In Bashiqa, about 10 miles north of Mosul, the first waves of a 2,000-strong peshmerga force entered the town on foot and in armoured vehicles or Humvees.

Isis fighters have sought to slow the offensive on their Mosul stronghold with waves of suicide car bomb attacks, burning of oil heads and artillery shells containing mustard gas.

To the south of Mosul, security forces said they had recaptured and secured the town of Hammam al-Alil from Isis fighters, who they said had kept thousands of residents as human shields as well as marching many others alongside retreating militants towards Mosul as cover from airstrikes.